|Publication number||US7717694 B2|
|Application number||US 11/853,660|
|Publication date||May 18, 2010|
|Filing date||Sep 11, 2007|
|Priority date||Sep 11, 2007|
|Also published as||US7862767, US20090065963, US20100181700|
|Publication number||11853660, 853660, US 7717694 B2, US 7717694B2, US-B2-7717694, US7717694 B2, US7717694B2|
|Inventors||Robert A. Coleman, Timothy D. King|
|Original Assignee||Spirit Aerosystems, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (32), Classifications (8), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates to composite materials. More particularly, the invention relates to tensioning composite material during a curing process.
2. Related Art
Composite parts for use in airplanes and other applications may be made from braided preform composite material that undergoes forming and curing processes. Forming and curing processes may involve, for example, severing a piece of braided preform composite material from a mandrel; securing the material to a mold, such as a cure tool surface; impregnating the material with resin; positioning an airtight lining, such as a cure bag, over the composite material and resin; creating a vacuum between the airtight lining and the mold surface to compress the material and resin; and applying heat to the material, resin, and airtight lining. The mold may include a C-channel, typically comprising an elongated channel with a bottom wall, an inner upwardly extending side wall, and an outer upwardly extending side wall.
The C-channel can be curved in various planes, and the upwardly extending side walls may be integrally formed or otherwise joined to the bottom wall at 90° angles or non-90° angles. In one instance, the C-channel is curved along its length with the inner wall formed along an inner radius of the curve and the outer wall formed along an outer radius of the curve. When material is pressed against inner surfaces of the C-channel and then tensioned and compressed, undesirable wrinkles or aberrations can form in the material. This is due to the difference in path lengths between the material at the inner radius of the curve and the material at the outer radius of the curve. These wrinkles are more pronounced closer to a side edge of the material along the inner radius. In a curved C-channel, wrinkles typically form along the inner wall.
A method and apparatus for tensioning a material over a mold to eliminate the formation of wrinkles, depressions, or other aberrations during vacuum compression is disclosed. According to this method, at least one tensioning fork is positioned against at least a portion of the material to exact tension on the material when force is applied to the tensioning fork.
In various embodiments, the tensioning fork has a first tapered leg, a second tapered leg, and a joining arm. The tapered legs each have a wide end and a narrow end and are tapered in a generally conical manner. An elongated portion of each tapered leg may be generally flat on one side. The joining arm spans the distance between the first tapered leg and the second tapered leg, such that the legs are fixed substantially parallel to each other. At least one of the tapered legs is pivotally secured to the joining arm.
The method of using the tensioning fork to tension material comprises the steps of forming material over a mold, such as a cure tool; positioning the first tapered leg between the mold and the material; and positioning the second tapered leg against a top face of the material. Next, the method comprises the steps of positioning a force-exacting component, such as an airtight lining, over the mold and material combination and exacting force on the second leg by compressing the force-exacting component toward the mold. This compression force urges the second leg to pivot towards the mold, thereby pressing a portion of the material against the mold to tension the material disposed between the first leg and the second leg. The final step of the method comprises applying heat to cure the material.
Preferred embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein,
The diameters of the tapered legs 18,20 may be determined by the material area and density requiring tension. For example, if the material 12 needs 0.250″ added tension, the maximum diameter of the first leg 18 would be about 0.250″ to 0.270″. The diameters at the narrow ends 28,30 of the tapered legs may be as small as possible without creating a point sufficiently sharp to puncture the force-exacting component 16.
The joining arm 22 of the tensioning fork 10 is operable to allow at least one of the legs 18,20 to pivot about the other leg 22,20 along a length of the leg, as illustrated in
Because the tensioning fork 10 is positioned on the material 12 in the method of the present invention, a description of the material 12 and its positioning over the mold 14 is provided. The material 12 tensioned by the fork 10 is positioned over the mold 14, such that the material 12 has a bottom face 34 oriented towards the mold 14, a top face 36 oriented away from the mold 14, first and second end edges 38,40, and first and second side edges 42,44. Material 12 is commonly a composite material that is generally pliable, such as a braided preform. The mold 14 may be a cure tool, though other types of molds may be used.
The C-channel's walls 50,52 may be fixed or positioned relative to the bottom wall 48 of the C-channel 46 at 90° angles. Alternatively, as illustrated in
In operation, the tensioning fork 10 of the present invention is used in a method comprising the steps of forming the material 12 over the mold 14; positioning the tensioning fork 10 against the material 12; positioning a force-exacting component 16, such as a cure bag, over the mold 14 and material 12 combination; exacting a vacuum force to compress the force-exacting component 16 and material 12 to the mold 14; and applying heat to cure the material 12. Referring to
Next, the tensioning fork 10 is positioned against the first side edge 42 of the material 12 proximate to the first end edge 38 of the material. The joining arm 22 of the tensioning fork 10 is adjacent the first side edge 42 and the legs 18,20 extend generally perpendicular to a length of the material 12. Thus, a portion of the material 12 is interposed between the legs 18,20 of the tensioning fork 10, as illustrated in
The force-exacting component 16, such as a cure bag or airtight liner, is then positioned over the mold 14 and material 12 combination. The force-exacting component 16 illustrated in
Once the force-exacting component 16 is substantially sealed to the mold 14, a vacuum force removes air between the mold 14 and the force-exacting component 16, thereby compressing the force-exacting component 16 and material 12 to the mold 14. The force exacted by the force-exacting component 16 is sufficient to hold the tensioning forks 10,68 against the mold 14. The force exacted by the compressed force-exacting component 16 may be approximately 90 psi.
When a force, such as compression force of a cure bag, is applied to the second leg 20 of the tensioning fork 10, the second leg 20 pivots inwardly and towards the mold 14, pressing a portion of the material 12 against the mold 14. The first leg 18 is disposed between the mold 14 and the material 12, so at least part of the first leg 18 protrudes outward from the plane of the mold 14, creating a bulwark across which the material 12 is tensioned. Therefore, during compression, the second leg 20 forces the material 12 towards the mold 14 while the first leg 18 forces the material 12 away from the mold 14. Thus, the second leg 20 exacts force in one direction on the material 12 while the first leg 18 exacts force on the material 12 in the opposite direction, thereby tensioning the material 12.
In relation to the curved C-channel 46, the tensioning forks 10,68 are positioned on the first side edge 42 of the material 12 adjacent to the inner wall 50 of the C-channel 46. Because the C-channel 46 is curved, it has a shorter path length at the inner radius 58 and a longer path length at the outer radius 60. This results in excess fabric forming vertical wrinkles or aberrations along the inner radius 58 of the curve during compression. Therefore, the tapered legs 18,20 provide tension closest to the first side edge 42 of the material 12 along the inner wall 50. More specifically, the wide ends 24,26 exact a greater amount of tension at the first side edge 42 of the material 12 adjacent the inner wall 50, and the narrow ends 28,30 exact a smaller amount of tension closer to the material 12 adjacent the bottom wall 48 of the C-channel 46, where less additional tensioning is required.
After compression, heat is applied to the force-exacting component 16, the material 12, and the tensioning fork 10 during a cure process.
Although the invention has been described with reference to the embodiments illustrated in the attached drawings, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims. For example, the first leg 18 of the tensioning fork 10 can be integral to the mold 14 as opposed to the fork 10 being a unitary, separate structure. Referring to
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|U.S. Classification||425/389, 425/472, 425/468|
|Cooperative Classification||B29C70/30, B29C70/44|
|European Classification||B29C70/44, B29C70/30|
|Sep 12, 2007||AS||Assignment|
Owner name: SPIRIT AEROSYSTEMS, INC., KANSAS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:COLEMAN, ROBERT A.;KING, TIMOTHY D.;REEL/FRAME:019815/0026;SIGNING DATES FROM 20070821 TO 20070827
Owner name: SPIRIT AEROSYSTEMS, INC.,KANSAS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:COLEMAN, ROBERT A.;KING, TIMOTHY D.;SIGNING DATES FROM 20070821 TO 20070827;REEL/FRAME:019815/0026
|Aug 24, 2009||AS||Assignment|
Owner name: BANK OF AMERICA, N.A., AS COLLATERAL AGENT,CALIFOR
Free format text: PATENT SECURITY AGREEMENT;ASSIGNOR:SPIRIT AEROSYSTEMS, INC.;REEL/FRAME:023134/0318
Effective date: 20090818
|Apr 19, 2012||AS||Assignment|
Owner name: SPIRIT AEROSYSTEMS, INC. (FKA MID-WESTERN AIRCRAFT
Free format text: TERMINATION AND RELEASE OF SECURITY INTEREST IN PATENTS;ASSIGNOR:BANK OF AMERICA, N.A., AS COLLATERAL AGENT (INCLUDING AS SUCCESSOR COLLATERAL AGENT TO CITICORP NORTH AMERICA, INC.);REEL/FRAME:028072/0314
Effective date: 20120418
Owner name: BANK OF AMERICA, N.A., AS COLLATERAL AGENT, CALIFO
Free format text: NOTICE OF GRANT OF SECURITY INTEREST IN PATENTS;ASSIGNOR:SPIRIT AEROSYSTEMS, INC.;REEL/FRAME:028072/0647
Effective date: 20120418
|Oct 23, 2013||FPAY||Fee payment|
Year of fee payment: 4